I don't know much about lightning, but I still assume that you have to get the bitcoin somehow in the first place. Right now, if I buy 1mil of bitcoin with my fiat,   about 200K will go into transaction fees. So the only way is to buy so much that the transaction fee becomes a small percentage. Am I wrong?
 

 If you want a self-custodial Lightning wallet, using something like Phoenix will require at least a minimum amount to create the wallet.

If you don't mind KYC, and live in a country where it's compatible (U.S. and El Salvador), Strike is a good one.